en. xxxiii. GASEOUS NEBULsE. 327 



spectrum, because some light is absorbed by the vapours in 

 our atmosphere. Now, when Miller and Huggins examined 

 the light which comes from Jupiter, they found three or four 

 lines like those caused by our atmosphere, showing that 

 Jupiter must have an atmosphere partly, but not entirely like 

 ours. Mars and Saturn also both showed these atmospheric 

 lines, and so did Saturn's rings, proving that a similar atmo- 

 sphere must spread over them also. But our moon gave none 

 of them, and this agreed with other evidence in showing that 

 the moon has no atmosphere. 



They next passed on to examine the light of the stars, and 

 this was by no means an easy task, because the stars are so far 

 off that their light is very faint and difficult to catch. Never- 

 theless they proved that round one star, called Aldebaran 

 (No. 5, Plate I.), there must bean atmosphere of hydrogen, 

 sodium, magnesium, calcium, iron, tellurium, antimony, bis- 

 muth, and mercury, and you will notice that the last four of 

 these are not found in the sun. In the light of the star 

 Betelgeux, in the constellation Orion, and in another star, 

 called /3 Pegasi, no hydrogen is found, but it is found in all 

 the other stars, together with many other substances. In 

 some of the stars there are besides, lines which are not found 

 by the burning gas of any known substances on our earth. 



Dr. Huggins proves that some Nebulas are Gaseous, 

 1864. And now we come to a very interesting experiment. 

 You will remember that astronomers doubted Sir W. 

 Herschel when he suggested (p. 275) that some of the 

 nebulae are not made of tiny stars, but of gas which is 

 forming into stars. In 1864 Dr. Huggins began to examine 

 these nebulae with the spectroscope, and he found that they 

 did not give a band of colour with dark lines upon it as the 

 stars do, but a few faint lines on a dark ground, exactly as 



